The SEP article on idealism begins:

... [this article] examines the relationship between epistemological idealism (the view that the contents of human knowledge are ineluctably determined by the structure of human thought) and ontological idealism (the view that epistemological idealism delivers truth because reality itself is a form of thought and human thought participates in it).

If realism is just the antonym of idealism then:

  • Epistemological realism is the view that contents of human knowledge are not ineluctably determined by the structure of human thoughts
  • Ontological realism is the view that reality itself is not a form of thought which human thought participates in

Please correct me if the realist terms are not often used that way, because wikipedia seems to say that they aren't, that the former assumes the latter.

Epistemological realism is a philosophical position... holding that what you know about an object exists independently of your mind.

My question is: how are the two realisms, defined as they are above, related? Are there any strong arguments for deriving one from the other?

  • actually i think "epistemological realism" does tend to include its ontological form. but the questions stands
    – user6917
    Commented Jan 3, 2016 at 22:56
  • 1
    I hope someone has a good answer. I am not sure that "realism" has a consistent definition. Platonists can be "realists" about ideas. It would seem to me that realism as "mind independence" can qualify ontology but not epistemology. So the two cases are not the same. Epistemological idealism may or may not imply ontological idealism, but "realist" epistemology and ontology more or less collapse into one another. But I need to think about it more. Something is off here. Commented Jan 4, 2016 at 0:08
  • @NelsonAlexander ep. realism traditionally means ont. r. and that we can have knowledge of it (beyond, i suppose, that it exists). which does raise the question whether ep. r. as a i defined it, is an independent thesis. it is independent of ont. idealism, anyway, according to SEP
    – user6917
    Commented Jan 4, 2016 at 0:16
  • If we can know anything mind-independent (epistemological realism of qualia), it has to be knowledge of something mind-independent (ontological realism of essentia).
    – Philip Klöcking
    Commented Jan 4, 2016 at 0:19
  • @PhilipKlöcking not sure i follow you. i think if we can know something mind independently, there has to be something mind independent. but perhaps e.g. our knowledge is determined by something it isn't about
    – user6917
    Commented Jan 4, 2016 at 0:23

4 Answers 4


They are related in the same way as for idealism, epistemology provides a necessary foundation for ontology, if not strictly logically then morally. It is logically possible to be ontological realist while maintaining epistemological idealism, in fact it is attractive for its subtlety, Kant and Quine are famous examples. But they confirm the rule: if one does not believe that available experience (be it purely empirical or augmented by some sort of intuition) can more or less reveal reality "as it is" ontological realism becomes a formality.

For all Kant lets on about "things in themselves", for example, it is unclear if we should even refer to "them" in the plural, "they" might as well be the Parmenides's One. Quine writes in Theories and Things:

"The scientific system, ontology and all, is a bridge of our own making... But I also expressed my unswerving belief in external things — people, nerve endings, sticks, stones. This I reaffirm. I believe also, if less firmly, in atoms and electrons and classes. Now how does all this robust realism reconcile with the barren scene I have been depicting?"

That would be with the barren scene of unknowable ontology due to indeterminacy of translation. It does only by redefining "real" as indispensable in our current conceptual scheme, "to be is to be a value of a variable", as Quine puts it. Putnam experimented with "internal realism" of this sort, but gave up on it.

What seems to be at play here is that the (naive) realist position still emotionally appeals to most people, including most scientists, no matter how untenable and indefensible it has become. So rather than give up the name many philosophers prefer to redefine the term, and then show that their version can be made compatible with the colloquial usage. That may be so, but this Wittgensteinian move certainly radically redefines the original meaning of "realism".

Realism is under so much pressure these days that even sophisticated realists, who try to stay closer to the original meaning, are forced to accept large doses of epistemological idealism. E.g. structural realists admit that objects of ontology themselves are inaccessible to us, and only relations among them are reflected in isomorphic structures of our scientific theories. See Worrall's Miracles and Models, where he argues that structural realism is the closest defensible option, but even it has to be accepted as default and defended, rather than positively promoted.


"Epistemological realism" is widely used today as I quote from the wikipedia article. So not just the rejection of epistemological idealism, though wikipedia at least says the former amounts to its rejection.

"Ontological realism" is can be used to mean the thesis that something real exists.

As pointed out in the comments, the latter entails a weak rejection of epistemological idealism.

Rejecting epistemological idealism entails a rejection of ontological idealism:

a commitment to ontological idealism obviously includes commitment to epistemological idealism since, assuming it allows for the possibility of knowledge at all, it allows nothing but the mental to be known

But not vice versa

there are many good reasons for epistemological idealism, indeed, that—suitably broadly understood—it has in fact become the default epistemology of modern philosophy, many of the most important of modern idealists have sought to avoid any inference from epistemological to ontological idealism.

Interestingly, the article concludes:

In fact, we might suggest in closing, the main alternative to what is essentially the epistemological idealism of a great deal of twentieth-century philosophy has not been any straightforward form of realism, but rather what might be called the “life philosophy” originally pioneered by Wilhelm Dilthey (1833–1916), then extensively developed by Martin Heidegger (1889–1976), and, without Heidegger’s political baggage, by the French philosopher Maurice Merleau-Ponty (1908–1961). The central idea of this approach to philosophy is that the starting-point of thought and knowledge is neither anything “subjective” like sense-data or ideas nor anything simply objective like the objects of science, but the lived experience of “being-in-the-world”


At the beginning of the twenty-first century, however, idealism, understood as a philosophical program, may be sharing the fate of many other projects in the history of modern philosophy. Originally conceived in the middle of the eighteenth century as a real alternative to materialistic and naturalistic perspectives, it may now become sublated and integrated into views about the nature of reality that ignore metaphysical oppositions or epistemological questions connected with the assumption of the priority of mind over matter or the other way round. Instead the focus may be shifting to establishing a “neutral” view according to which “anything goes” (Feyerabend) as long as it does not contradict or at least is not incompatible with our favored metaphysical, epistemological and scientific (both natural and social) methods and practices.


I read through the SEP article and found that (as usual) there has been terminological confusion in the first place.

A better find from the SEP article on idealism may be:

  1. something mental (the mind, spirit, reason, will) is the ultimate foundation of all reality, or even exhaustive of reality, and

  2. although the existence of something independent of the mind is conceded, everything that we can know about this mind-independent “reality” is held to be so permeated by the creative, formative, or constructive activities of the mind (of some kind or other) that all claims to knowledge must be considered, in some sense, to be a form of self-knowledge.

Idealism in sense (1) may be called “metaphysical” or “ontological idealism”, while idealism in sense (2) may be called “formal” or “epistemological idealism”.

And later on:

If one accepts this characterization, then ontological idealism is meant to be opposed to both dualism, according to which reality ultimately consists not just of mental “stuff” but also of mind-independent matter, and to materialism, which takes matter to be all there is, while epistemological idealism is opposed to materialism but not necessarily to dualism.

Realism as a whole is neatly defined in the article on metaphysical realism:

Metaphysical realism is the thesis that the objects, properties and relations the world contains exist independently of our thoughts about them or our perceptions of them.

In the article on Realism there is a twofold definition, first of what can be considered ontological realism:

First, there is a claim about existence. Tables, rocks, the moon, and so on, all exist, as do the following facts: the table's being square, the rock's being made of granite, and the moon's being spherical and yellow.

And a definition of what might reasonably be called epistemologic realism:

The second aspect of realism about the everyday world of macroscopic objects and their properties concerns independence. The fact that the moon exists and is spherical is independent of anything anyone happens to say or think about the matter. Likewise, although there is a clear sense in which the table's being square is dependent on us (it was designed and constructed by human beings after all), this is not the type of dependence that the realist wishes to deny. The realist wishes to claim that apart from the mundane sort of empirical dependence of objects and their properties familiar to us from everyday life, there is no further (philosophically interesting) sense in which everyday objects and their properties can be said to be dependent on anyone's linguistic practices, conceptual schemes, or whatever.

It has to be considered that there obviously are major glitches between the epistemological/ontological divide in idealism as defined and the respective divide in realism. The SEP article on realism states just before the definitions given:

There are two general aspects to realism, illustrated by looking at realism about the everyday world of macroscopic objects and their properties.

This is supported by the definition of metaphysical realism, which includes both aspects. That means it is implicated that in order to be a "real" (harhar) realist, you have to endorse both aspects, which corresponds to the fact that Kant called himself transcendental idealist, albeit being an ontological realist (highlighted in the article on idealism, too). The ontological idealist on the other side is an idealist in the strongest sense and has by definition have to be epistemological idealist. And an ontological realist does not have to deny the independent existance of thoughts, that would be materialists.


So basically, following these definitions, someone who says that facts exist independent from our thoughts, i.e. we can unalienated by human thought or perception know of them, have to presuppose fact-constituting existance that is mind-independent. Ergo, epistemological realists have to be ontological realists (and only then are full-blooded realists), epistemological idealist can be.

  • that explains our confusing discussion, thanks
    – user6917
    Commented Jan 4, 2016 at 3:52

I had the same question and think that Drummond clarifies this issue brilliantly: Drummond, J.J. (2012): "Husserlian Intentionality and Non-Foundational Realism: Noema and Object", Springer Science & Business Media, pages 253-254 and 258.

Here’s the link to the passages: https://books.google.co.uk/books?id=osu3BgAAQBAJ&pg=PA253&lpg=PA253&dq=J.J.+Drummond+ontological+realism+epistemological+realism+independent+mind&source=bl&ots=zCjFpHq0s-&sig=SL_gVXi9c4P44-u536yfo6W76XM&hl=en&sa=X&ved=0ahUKEwjO9P2jz5DLAhVMvBQKHcUMAfEQ6AEIIzAB#v=onepage&q=J.J.%20Drummond%20ontological%20realism%20epistemological%20realism%20independent%20mind&f=false

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    Welcome to Philosophy.SE! Can you summarize the passage, just in case Google decides to take their books site down? (Maybe unlikely, but it happened to Buzz, Reader, and others....) Commented Feb 24, 2016 at 22:57

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